1. Field of the Invention
This invention relates to measuring systems and, in particular, to a measuring system which automatically provides measurements of selected dimensions of a wide variety of objects.
2. Prior Art
The measurement of dimensions of objects is of importance in a wide variety of fields. For example, in steel mills the lengths of steel slabs must be measured. On highways, the length of trucks must be measured to insure compliance with the motor vehicle laws. Freight haulers measure the volume of freight, as well as its weight, to calculate shipping charges. In lumber mills accurate measurements of log dimensions are necessary to select the most efficient cutting pattern for each log.
Various techniques have been proposed to measure the dimensions of objects automatically. In one system, mirrors rotate at a uniform rate and reflect light to a sensor from the object whose length is being measured. The number of light pulses generated by the sensor, together with the rotational rate of the mirror and the velocity of the object, uniquely determine the length of the object. The rotating parts, however, require frequent maintenance and adjustment.
Other automatic dimension measuring apparatus have been the subject of several patents. See, e.g., U.S. Pat. No. 3,897,156 entitled "Structure for Measuring the Average Diameter of an Approximately Circular Cross-Section of an Object," by Leon H. Chasson and assigned to Atmospheric Sciences, Inc., and U.S. Pat. No. 3,787,700 entitled "Automatic System for Measuring Selected Dimensions," also invented by Chasson and assigned to Atmospheric Sciences, Inc., the assignee of the invention which is the subject of this application. Also U.S. Pat. No. 3,806,253 entitled "Sweep Measuring Scheme" issued on an application of Denton and assigned to Weyerhaeuser Company, discloses a method of determining the sweep of a log.